Microsoft SharedView Public Beta
Previously known as Codename "Tahiti", SharedView is now in public beta!

Think of SharedView as a free, lightweight version of Microsoft Office LiveMeeting that supports up to 15 participants sharing and collaborating on documents, spreadsheets, powerpoint presentations and whatever else. Another cool feature is the ability for the participants to share handout's which eliminates the need to email during/after the session.
I've used SharedView several times now to help/remote control PC's for friends and family - it works extremely well. Very easy to send an invitation using email, IM, or VOIP.
Download the latest beta code from here.